Dissolved copper-complexing ligands in cultures of marine bacteria and estuarine water

We have determined concentrations and conditional stability constants of dissolved copper-complexing ligands in chemostat cultures of autotrophic (Synechococcus) and heterotrophic (Vibrio) marine bacteria, and in estuarine waters. Ligands with high affinity for copper were detected in Vibrio and Synechococcus cultures, and ligand production by Vibrio was dependent on the copper concentration in the medium. While Synechococcus cultures produced ligands in excess of the copper concentration, Vibrio ligands were copper-saturated in the growth medium. Synechococcus cultures produced ligands at concentrations of 2 μM when the copper concentration was incrementally increased in the chemostat. Copper-complexing ligands were quantitatively removed from an estuarine water sample utilizing a modified immobilized copper ion affinity chromatography (IMAC) protocol. The ligands were recovered from the column by elution with either acidified, UV oxidized seawater or with a glycine eluent. These results show that heterotrophic bacteria have the potential to contribute to the pool of strong copper-complexing ligands in natural waters and that relatively high concentrations of these ligands can be produced in cultures. Improvements in the IMAC protocol for isolation of copper-complexing ligands are promising for their isolation and purification from natural waters and cultures.